a. Field
The instant disclosure relates generally to ablation electrode assemblies and, in particular, to ablation electrode assemblies with improved irrigation of the assembly and ablation site.
b. Background Art
Electrophysiology catheters are used in a variety of diagnostic and/or therapeutic medical procedures to diagnose and/or correct conditions such as atrial arrhythmias, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmias can create a variety of conditions including irregular heart rhythms, loss of synchronous atrioventricular contractions and stasis of blood flow in a chamber of a heart which can lead to a variety of symptomatic and asymptomatic ailments and even death.
A medical procedure in which an electrophysiology catheter is used includes a first diagnostic catheter deployed through a patient's vasculature to a patient's heart or a chamber or vein thereof. An electrophysiology catheter that carries one or more electrodes can be used for cardiac mapping or diagnosis, ablation and/or other therapy delivery modes, or both. Once at the intended site, treatment can include application of, for example, radio frequency (RF) ablation, cryoablation, laser ablation, chemical ablation, high-intensity focused ultrasound-based ablation, microwave ablation. An electrophysiology catheter imparts ablative energy to cardiac tissue to create one or more lesions in the cardiac tissue and oftentimes a contiguous or linear and transmural lesion. This lesion disrupts undesirable cardiac activation pathways and thereby limits, corrals, or prevents errant conduction signals that can form the basis for arrhythmias.
During RF ablation, local temperature elevation can result in coagulum formation on the ablation electrode, resulting in a local impedance rise. As the impedance increases, more energy is passed through the portion of the electrode without coagulum, creating even higher local tissue temperatures and further increasing coagulum formation and the impedance. Finally, enough blood coagulates onto the electrode that no energy passes into the targeted tissue, thereby requiring the catheter to be removed from the vascular system, the electrode to be cleaned, and the catheter to be repositioned within the cardiac system at the desired location. Not only can this process be time consuming, but it can be difficult to return to the previous location because of the reduced electrical activity in the tissue, which has been previously ablated. Recent studies have also demonstrated the formation of a so-called soft thrombus in RF ablation. The formation of the soft thrombus results from heat induced protein denaturation and aggregation and occurs independently of heparin concentration in serum. In addition, RF ablation can generate significant heat, which, if not appropriately controlled, can result in excessive tissue damage, such as tissue charring, steam pop, and the like.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.